Warm air furnace



Oct. 31, 1961 R. W. NEWELL WARM AIR FURNACE Filed April 27, 1959 4 L I e 2 Sheets-Sheet 2 2e, ss Y a! 7 5 as f l2 1 l FIG. 4

2.2. I 34 INVENTOR ROBERT W. NEWELL. 0 2.9

, H rs ATTORNEY United States Patent ()fllice 3,006,334 Patented Oct. 3 1, 1961 3,006,334 WARM AIR FURNACE Robert W. Newell, Yardley, Pa., assignor to General Electric Company, a corporation of New York Filed Apr. 27, 1959, Ser. No. 809,120 2 Claims. (Cl. 126-110) The present invention relates to warm air furnaces for domestic heating systems. The invention is particularly concerned with a forced air furnace so designed that it can be installed and'will operate properly in either a downflow position or a horizontal position.

In both downflow and horizontal forced air furnaces, the forced flow of air over the heat exchanger as indicated by the terms downflow and horizontal is different from the upward flow which results from gravity circulation of the air over the heat exchanger. Because of this fact, the designs of forced air furnaces known prior to the present invention have been such that downflow and horizontal furnaces were not interchangeable or in other words a downflow furnace could not be operated satisfactorily in a horizontal position and vice versa. The principal reason for this has been that both the structure and the intended operating position of a warm air furnace determines the locations of the temperatureresponsive switch mechanisms controlling the operation of the air circulating blower and the burner required to assure proper and safe operation of the furnace. For example, the switch mechanism controlling the operation of the air circulation fan or blower includes a heat sensing element that must be located to sense radiant heat from the heater and energize the blower under gravity air flow conditions, that is the condition existing before air circulation is established by the blower, but must not be unfavorably afiected by the air from the blower after forced circulation has once been established. Further, to protect either a downflow furnace or a horizontal furnace, one or more limit control switches must also be provided to stop the burner when the air temperatures within the furnace casing become excessive either when the blower is operating or when it is idle. Thus this safety feature requires not only a sensing of the temperature of the discharge air under forced air circulation in order to stop the burner if the temperature of the forced air becomes excessive but also a sensing of excessive temperatures in the event the forced air circulation system fails for any reason. In addition, the limit controls must he so arranged that the control circuit will not stop the burner before the blower control switch initiates operation of the blower.

Because of the conflicting control problems resulting from the fact that the forced air circulation through either a downflow furnace or a horizontal furnace is different from gravity circulation and the fact that the gravity circulation of air in a downflow furnace is different from that in a horizontal furnace, the structure and control arrangements of presently available furnaces are such that a furnace designed for downflow forced air circulation will not operate properly in a horizontal position while a furnace designed for horizontal operation will not function properly if supported in such a manner that the forced air inlet or return is at an elevation substantially higher than the forced air outlet or discharge opening.

It is a primary object of the present invention to provide a forced air furnace so constructed and arranged that, Without any substantial or major alterations, it can be operated in either a downflow or horizontal position, the horizontal position being attained by turning the furnace over from its vertical position onto either side.

It is'a further object of the invention to provide a furnace including a heat exchanger unit of a construction which permits the placement of the fan and limit control means in such positions relative to the heat exchanger that the furnace will operate safely and properly in either a downflow or a horizontal position.

Further objects and advantages of the invention will become apparent as the following description proceeds, and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In accordance with the present invention, there is provided a forced air furnace including a casing, a heater or heat exchanger unit disposed within the casing and means including a blower or equivalent air circulating means for circulating air through the casing and over the heater and discharging the heated air from the casing into a suitable duct system or space to be heated. The heat exchanger unit is disposed adjacent the air outlet end of the casing and extends somewhat over one-half the distance to the opposite end of the casing where it is connected to a flue disposed at about the mid section of the casing. A burner is positioned within the heat exchanger unit adjacent the end opposite the flue connection or in other words in the end of the heat exchanger unit disposed adjacent the air outlet end of the casing. In order to control the opera tion of the furnace when mounted in either downflow position in which the air outlet end forms the base of the furnace or in a horizontal position, there is provided a first temperature responsive fan and limit switch arranged adjacent the unit between the burner and the flue connection to sense the temperature of the unit when the blower is not operating and to sense the temperature of the air flowing from the blower over the unit when the fan is operating. A second temperature responsive limit switch is arranged adjacent the flue connection and is adapted to de-energize the burner whenever the temperature sensed thereby exceeds a safe operating limit either when the fan or blower is operating or stopped.

For a better understanding of the invention reference may be had to the accompanying drawing in which:

FIG. 1 is an elevational view illustrating the position of the furnace for downflow operation;

FIG. 2 is a view similar to FIG. 1 showing the furnace mounted on one of its two sides for horizontal operation;

FIG. 3 is a somewhat diagrammatic view, partially in section, of the furnace of the present invention showing the internal structure and arrangement thereof;

FIG. 4 is a sectional view taken along line 44 of FIG. 3; and

FIG. 5 is a simple wiring diagram illustrating one type of control system suitable for the operation of the furnace of the present invention.

Referring now to the drawings, the furnace of the present invention comprises a generally rectangular casing 1 including side walls 2 and 3 and end walls 4 and 5. The furnace can rest on either side walls, 2 or 3, for horizontal operation or on end wall 5 for downflow or vertical operation. The one end wall 4 which forms the top of the furnace when it is mounted vertically for downflow operation or one horizontal end of the furnace when mounted horizontally includes a return air inlet 6 for receiving air to be heated while the opposite end wall 5 includes .a heated air outlet 7. A blower 9 mounted within the inlet end of the casing draws return air through the inlet 6 and circulates this air over a heat exchanger unit generally indicated by the numeral 10, the heated air leaving the casing through the outlet 7.

In order that the furnace of the present invention will operate satisfactorily in either the downflow or horizontal position, the heat exchanger '10 is so designed and so positioned within the casing 1 that the required control elements can be so associated as to sense their desired operating temperatures. As shown in FIGS. 3 and 4 of the drawing, this unit 10 comprises a closed cylindrical section 11 including cylindrical side walls -12 and end walls 14 and 15. The section is arranged within the furnace casing 1 with the end wall 14 adjacent and in spaced relationship with the air outlet7. The heat exchanger also includes a second section of a hollow annular construction 17 which surrounds the section 11 adjacent the other end wall 15 in spaced relationship with the cylindrical wall 1 2. The two sections 11 and 17 are connected adjacent the rear side of the furnace by means of a conduit 19. An opening 21 surrounded by a flange 22 provides means for inserting into the heat exchanger section 11 a heating unit including a fluid fuel burner generally indicated by the numeral 23 and a combustion chamber 24. The combustion chamber 24 as illustrated in FIGS 3 and 4 of the drawings is of a box-like structure having openings 25 on the top'and on the side thereof facing the end wall 14 whereby the products of combustion from the burner 23 are directed upward and also downward towards the end wall 14 as they issue from the opening 25. A layer of heat resistant tile or the like 26 provided on the end wall 14 protects this wall from the products of combustion of the burner unit 23. These combustion products flow through the heat exchanger section 11 and the conduit 19 into and through the hollow annular section -17 and out of the furnace by way of the flue connection 29 provided at the front of the casing 1, which connection is positioned at about the mid section of the casing 1.

. Means for supporting the heat exchanger unit within the casing -1 includes a main structural member 30 in cluding a front panel 31 forming part of the front wall of the furnace and a transverse panel 32 on which the fan or blower 9 is supported. This structural member 30 extends from side to side of furnace casing and is suitably secured to the end wall and the rear structure of the casing in such a manner that along with the walls, i-t substantially supports the weight of the heat exchanger unit and the burner assembly when the furnace is either in the vertical downflow position or in the horizontal position. The cylindrical section 11 of the heat exchanger unit-is connected by means of the. flanges 22 to the front panel 3-1 of the structural member while theflue connection29 which passes through the structural member provides means for connecting the annular section 17 of the heat exchanger unit. Surrounding the heat exchanger unit within the casing is the radiation shield 33 which envelops the burner end of the cylindrical section 11 in spaced relation therewith and with the walls of the casing and which is connected to the cylindrical section by a plurality of supporting angle brackets 34. The radiation shield 33 may be secured at its forward ends to the panel 31 and along its rear section to the angle irons 38 which in turn are affixed to the casing 1 When the blower 9 is operating, air drawn through the return air inlet 6 by the blower is forced downwardly as shown in FIG. 3 through the blower outlet opening 40 in the panel 32 into the space defined by the structural member 30 and the rear wall and side walls of the casing 1. This air stream then flows around and in heat exchange relationshiP With the heat exchanger unit as in-. dica-ted by the solid arrows in FIG. 3 of the drawing. More particularly, this air flow is both on the outside of the annular section 17 and also through the passageway 41 between section 17 and the cylindrical wall 12 of the section 11. The air then flows between the cylindrical wall 12 and the radiation shield 33 where it picks up additional heat from these elements before passing out of the outlet 7 provided in the end 5 of the casing.

The path of the forced air flow through the furnace is the same whether the furnace is mounted for downflow operation or is horizontally mounted on one or the other of its two sides 2 or 3 for horizontal operation as shown in FIG. 2 of the drawing. However, gravity air flow through the furnace, that is the air flow resulting from the operation of the burnerwhen the blower is not op; erating, depends upon whether the furnace is vertically or horizontally mounted. When vertically mounted for downflow operation, the normal or gravity flow of air'is upwardly through the furnace and is just the reverse of forced air circulation. On the other hand when the furnace is mounted in a horizontal position resting on either of its two sides there will be some gravity flow of air through the furnace even though both the inlet and outlet openings are at substantially the same level. Under these conditions the temperature surrounding the heat exchanger unit rises rather rapidly when theblower 9 is not operating.

The above-described structure of the heat exchanger unit 19 and its position within the casing 1 provides a solution to the divergent control problems resulting from the differences in gravity flow through the furnace when mounted in a vertical or a horizontal position. Specifically, it has been found that by mounting a fan and limit control switch 42 in a position in which its temperature responsive operating element 43 is disposed between the heat exchanger section 17 and the burner so that it will sense the temperature of the adjacent portion of the cylindrical heat section 11 when the fan 9 is not operating and will be in the path of the air flowing through the passage 41 when the fan is operating, this control will operate satisfactorily with the furnace in any one of its three intended operating positions (one downfiow, two horizontal). Likewise, by placing a limit switch 44 immediately adjacent the flue 29 so that its sensing element 45 is on the downstream side of the flue 29, this switch will operate satisfactorily to sense abnormal temperatures with the furnace in any one of its three intended positions.

The two switches 42 and 44 form part of an electrical control circuit schematically diagrammed in FIG. 5 of the drawing. This circuit includes a pair of supply conductors 5G and 51 leading from a switch 52 controlled by a thermostat and adapted to close in response to a call for heating of the enclosure. Upon closure of the switch 52 a circuit is established through the conductor 53, the burner 23, the normally closed limit switch 44 and the normally closed contact 54 forming part of the fan and limit switch 42 controlling the operation of, the burner 23. As will be more fully described hereinafter the fan and limit control switch 42 also includes a second contact 55 which upon a predetermined increase in temperature of the control element 45 will close a circuit including the blower 9- e V Returning to a more detailed consideration of the operation of the furnace, its operation when mounted in the downflow or vertical position will first be considered. Upon the call for heat, the burner 23 is first energized and with the burner operating the products of combustion issuing from the combustion chamber 25 gradually warm the cylindrical walls 12 of the heat exchanger unit. With the thermal control element 43 of the switch 42 in a position to sense this increase in temperature, the element causes the switch contact 55 to close and energize the blower 9 when the temperature of the heat exchanger element is such that Warm air will be delivered from the outlet 7 upon operation of the blower 9. Normally, the furnace will operate under control of only the CO1]? tacts 55 0f the switch 42 and the switch 52. Each time the switch 52 is actuated by thermostat during calls for heat, the burner is first energized. Thereafter, as a result of radiant and convected heat from the walls 12, the thermal element 43 will energize the blower circuit. When the thermostat requirements are satisfied, the burner 23 is de-energized and after the heat exchanger 12 has decreased in temperature to a predetermined point, the thermal element 43 will de-energize the blower circuit,

If for any reason the discharge air temperature becomes too high while the blower 9 is operating as, for example, by having the air flow through the furnace diminished due to an obstruction in the inlet or outlet opening or the duct systems connected thereto, the resultant abnormal rise in temperatures sensed by the thermal element 43 will cause the contacts 54 to open thereby to de-energize the burner 23. In order to protect the system in the event of blower failure, the switch 44 is so connected into the control circuit so that it will de-energize the burner under abnormal temperature conditions. In order that this switch be capable of providing the desired protection, the thermal element 45 forming part of this switch structure is positioned on the downstream side of the flue 29. It is in close proximity to the annular section 17 of the heat exchanger and is therefore primarily responsive to the temperature of the heat exchanger and the flue connection 29 and partially responsive to the air flowing through the furnace. In this position it will de-energize the burner whenever the temperatures sensed thereby become excessive and regardless of whether or not the blower 9 is operating at full or in partial capacity.

With the control switches 42 and 44 positioned as described, the same operation and the same protection is obtained when the furnace is mounted in its horizontal position on either the side 2' or the side 3. The switch 42 functions normally first to sense the increased temperature of the heat exchange element and energize the blower and under abnormal conditions to de-energize the burner in the event there is an abnormal increase in the temperature of the air being forced through the furnace structure. With the limit switch 44 partially responsive to the forced air flow due to its position with respect to flue 29 but nevertheless in a position to sense any abnormal increase in temperatures of the flue connection and other adjacent portions of the heat exchange element, this switch will open the burner circuit under abnormal static or air flow temperature conditions.

If desired and in order to provide a furnace which is completely interchangeable between the downflow and the horizontal positions, the upper portion of the casing which includes the access opening 60 for access to the blower 9 may be closed by a square panel 61 so that rotation of the panel will cause any trademark or other indicia on the panel to appear in the proper position.

While the present invention has been described with reference to the particular embodiment thereof, it will be understood that various modifications may be made by those skilled in the art without departing from the invention. The appended claims are therefore intended to cover all such modifications as come within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A furnace comprising a casing including side, front and end walls and having a return air inlet opening in one end wall and a heated air outlet opening at the other end wall, a heat exchanger unit within said casing, said unit comprising a closed first section in spaced relation with said casing and having one end disposed adjacent said other casing end wall in front of said outlet opening, said unit including a hollow second section surrounding and spaced from the other end of said first section at approximately the mid section of said casing, a flue connection on said second section, a burner disposed in said one end of said first section, a conduit connecting said first section with the second section for flow of combustion products from said first section to said second section, a blower positioned in said casing adja cent said one end wall for circulating return air through said casing and between said first and second sections and out of said casing through said air outlet, and temperature responsive means for controlling the operation of said blower and said burner and including a first thermal switch means having a thermal actuating element positioned within said casing adjacent said first section at a point between said second section and said burner for energizing said blower in response to an increase in temperature of said first section and for deenergizing said burner upon an excessive increase in the temperature of the air blown through the space between said sections and over said element by said blower, and a second thermal switch means having a thermal actuating element positioned between said casing and said second member adjacent to and responsive to the temperature of said flue connection and second member for de-energizing said burner upon an excessive increase in the temperature of said flue connection and second member when said blower is not operating, the positioning of said thermal actuating elements providing controlled operation of said furnace when said furnace is in either a vertical position resting on said one casing end wall or in a horizontal position resting on either of said casing side walls.

2. A furnace comprising a rectangular casing including front, end and side walls and having a return air inlet in one of said end walls and a heated air outlet at the other of said end walls, a heat exchnager unit within said casing, said unit comprising a closed cylindrical section in spaced relation with said casing and having one end disposed adjacent said other casing end wall in front of said outlet, said unit including a hollow annular section surrounding and spaced from the other end of said cylindrical section at approximately the mid section of said casing, a flue connection on the front side of said annular section, a burner disposed in said one end of said cylindrical section, a conduit connecting said cylindrical section with the rear portion of said annular section for flow of combustion products from said cylindrical section to said annular section, a blower positioned in said one end of said casing for circulating return air through said casing and between said cylindrical and annular sections and out of said casing through said air outlet, and temperature responsive means for controlling the operation of said blower and said burner and including a first thermal switch means having a thermal actuating element positioned within said casing adjacent said cylindrical section between said annular section and said burner for energizing said blower in response to an increase in temperature of said cylindrical section and for de-energizing said burner upon an excessive increase in the temperature of the air blown through the space between said sections and over said actuating element by said blower, and a second thermal switch means having a thermal actuating element positioned between said casing and said annular member adjacent to and responsive to the temperature of said flue connection and annular member for de-energizing said burner upon an excessive increase in the temperature of said flue connection and annular member when said blower is not operating, the positioning of said thermal actuating elements providing controlled operation of said furnace when said furnace is in either a vertical position resting on said one casing end wall or in a horizontal position resting on either of said casing side walls.

References Cited in the file of this patent UNITED STATES PATENTS 2,642,227 Ray June 16, 1953 2,658,503 Scheurer Nov. 10, 1953 2,776,797 Suesserott Jan. 8, 1957 2,862,666 Kriechbaum Dec. 2, 1958 2,865,364 Cutter Dec. 23, 1958 

